Russian, Turkish, and Iranian officials are scheduled to meet to discuss a new push for a peace effort in Syria tomorrow, though the death of the ambassador is likely to cast a pall over the talks. Putin says he is determined to know who “directed” the gunman.

It is unclear who attacker, identified as Turkish police officer Mevlut Mert Altintas, might be affiliated with, though state media claimed he shouted an al-Qaeda slogan after the attack, and other Turkish officials suggested he was in league with US-based cleric Fethullah Gulen, though Gulen has denied this. The gunman declared, in both Turkish and Arabic, that the attack was revenge for Aleppo.

Putin says he and Turkish President Recep Tayyip Erdogan have agreed to a joint investigation into the incident. He also reported he has ordered increased security at Turkish diplomatic facilities in Russia, and is urging other nations to step up the security of Russian embassies and consulates abroad. This is the first ambassador’s assassination since 1829 for Russia.